Collections in C#

Introduction

It is just like as array ,but always dynamic and can hold any values unlike array. It is a data structure that holds data in many different ways. The collection class is defined in the System.Collections namespace. There are five types of collections in data structure.

1.Hastable
2.Arraylist
3.Linkedlist
4.Stack
5.Queue

But mostly use of two types collections in C#,they are Hastable and Arraylist. Here we will discuss about only Hastable and Arraylist.

1. Hastable

Hastable have two values i.e. key(id) and item(value).

Why we use Hastable

If we want to stored data in two dimensional array at run time then we use Hastable. For example, a months name and his serial number and we can access there data using a key.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Collections;
namespace hastable
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
Hashtable hs = new Hashtable();
hs.Add("1", "January");
hs.Add("2", "Febuary");
hs.Add("3", "March");
hs.Add("4", "April");
hs.Add("5","May");
hs.Add("6", "june");
hs.Add("7", "July");
hs.Add("8", "August");
hs.Add("9", "September");
hs.Add("10", "October");
hs.Add("11", "November");
hs.Add("12", "December");
//MessageBox.Show(hs["8"].ToString());// print one value(August)
foreach (string k in hs.Keys)
{
MessageBox.Show(hs[k].ToString());//print all values
}
}
}
}

Now run the application.
Output (One value using key) looks like the below image.

Output (all values using foreach loop) looks like the below image.

code description